Help please

Manhwa. Isekaid to a princess. Shitty brother and father, everyone basically hates her ( i think it was because of her dead mother?) but when they found out she had a curse(?) and thought she was dying, they began to see her in a new light. She kept on vomitting blood. She kept on dreaming of the OG's past. If I remember right, she could sometimes speak to OG's soul, and she calls her sister/unnie. I think the ML was supposed to kill her, but then was slowly changing his mind.